Abstract

An interstellar “precursor” mission has been under discussion in the scientific community for at least 30 years. Fundamental scientific questions about the interaction of the Sun with the interstellar medium can only be answered with in situ measurements that such a mission can provide. The Innovative Interstellar Explorer (IIE) and its use of Radioisotope Electric Propulsion (REP) is being studied under a NASA “Vision Mission” grant. Speed is provided by a combination of a high‐energy launch, using current launch vehicle technology, a Jupiter gravity assist, and long‐term, low‐thrust, continuous acceleration provided by an ion thruster running off electricity provided by advanced radioisotope
electric generators. A payload of ten instruments with an aggregate mass of ∼35 kg and requiring ∼30 W has been carefully chosen to address the compelling science questions. The nominal 20‐day launch window opens on 22 October 2014 followed by a Jupiter gravity assist on 5 February 2016. The REP system accelerates the spacecraft to a “burnout” speed of 7.8 AU per year at 104 AU on 13 October 2032 (Voyager 1’s current speed is ∼3.6 AU/yr). The spacecraft will return at least 500 bits per second from at least 200 AU ∼30 years after launch. Additional (backup) launch opportunities occur every 13 months to early 2018. In addition to addressing basic heliospheric science, the mission will ensure continued information on the far‐heliospheric galactic cosmic ray population after the Voyagers have fallen silent and as the era of human Mars exploration begins.